Polyolefin tobacco smoke filters



Figl Dec. Z7, 1960 G. P. ToUEY ErAL 2,965,157

POLYOLEF'IN TOBACCO SMOKE FILTERS Filed June 7. 1957 FigZ POLYOL EFI NFl LTE R F Gear eRToue l gi Robert um wer-QH 1N ENToRs .RT NRNEYS UnitedStates Patent O 2,966,151 POLYOLEFI'N TOBACCO SMOKE FILTERS George P.Touey and Robert C. Mnmpower Il, Kingsport, Tenn., assignors to EastmanKodak Company, Rochester, N.Y., a corporation of New `Iersey Filed June7, 1957, Ser. No. 664,157

9 Claims. (Cl. 131-208) This invention relates to tobacco smoke filters.More particularly, this invention relates to improved filters forcigarettes, which filters are made from a polyolefin material of acertain character.

The subject of tobacco smoke filters has received considerable attentionin recent years. Numerous patents and publications on this subject haveappeared. In general, many of the prior art filters have been comprisedof wads or masses of short filaments or granules of various materialsfor filter purposes. Many of the tobacco smoke filters in the prior artare made from paper or the like materials. However, the prior artfilters have not been entirely satisfactory in some respects. Many ofthe filters are not particularly efcient and others, particularly thewad or mass-type of filters, may be objectionable because of the highpressure drop.

For tobacco smoke filters in addition to the capability of the filter tofilter out certain components, there are a number of other propertiesthat need to be taken into consideration. For example, a cigarettefilter should have an acceptable feel in the smokers mouth. That is, thefilter should be firm, not only initially, but it should not get soggyor detach from the cigarette. The lter should not have such a highpressure drop that the effort to draw smoke through the filter isnoticeable to the smoker. The filter should be economical to make andcapable of being made on automatic machinery or otherwise lend itself tomass production because a low cost item is needed in view of therelatively low price range of tobacco products of the class described.

In recent years certain cellulosic yarns have come into use to a largeextent for cigaretter filters and in certain instances have replacedpaper filters that have been used. While such yarn-type material gives acigarette filter much improved over many prior art filters and alsocomprises a material which works well in automatic machinery there arecertain disadvantages which may be encountered with such filters. Thatis, in cellulosic yarn filters the present manufacturing processesfrequently include the application of plasticizer to this yarn so thatthe filaments of the yarn may be bonded by plasticizer for impartingstiffness to the filter. This, of course, involves the requirement ofspray booths and the like apparatus for applying plasticizer. Inaddition, such prior art yarn filters have used wrappers for holding thefilters in shape. r in some instances, particularly where staple beryarn has been used for the filter it has been necessary to coat the yarnwith a cellulosic bonding or coating material. This coating wouldlikewise involve the use of spray apparatus and the like. Although thecellulosic filters first referred to exhibit a better efficiency thanmany of the prior art filters they are not as economical to manufacturenor as efficient as the filters of the present invention to be describedin the present application.

ln view of the current interest in filters of the class described, it isapparent that the development of an improved filer represents a highlydesirable result.

This invention has for one object to provide a more efficient and moreeconomical tobacco smoke filter. Another object is to provide acigarette filter which is not only relatively firm initially but whichdoes not get soggy or soft from mouth or smoke moisture. Still anotherobject is to provide a filter which because of its hydrophobicproperties does not dry the tobacco smoke. Still another object is toprovide a method for manufacturing improved filters as aforesaid. Otherobjects will appear hereinafter.

In the broader aspects of the present invention We have found thatcertain polyolefns may be made into continuous filaments. We have foundthat these continuous filaments may be highly crimped. That is, thecrimping may be much greater than heretofore applied to filter material.We have found that this high crimping permits the obtaining of arelatively rigid filter without plasticizer addition or without theaddition of a bonding material, such as the addition of cellulosicadhesive components heretofore described in the prior art. We have foundthat the crimped material of the present invention can be used inexisting automatic equipment if this is desired and the cigarettefilters made generally the same as is now customary. That is, the filterelement is finally enclosed in a wrapper before being inserted in thecigarette. On the other hand, we have found that the improved crimpedfilter material of the present invention may readily be fused on theoutside to form a self-sustaining filter element not requiring awrapper.

The polyolefin material which we prefer to use has a molecular weightabove 10,000 and below 1,000,000. Preferably the molecular weight of thepolyolefin material would be between 30,000 and 200,000. The softeningpoint of the polyolefin polymer which we prefer to use is between C. and160 C. Of the several polyolefin materials produced industrially weprefer those known as polyethylene and polypropylene. The structuralunit for polyethylene can be represented as:

The structural unit for polypropylene can be repre- Either low densitypolyethylene, namely polyethylenes having a softening point of about C.to 100 C. or high density polyethylenes which have a softening point ofC. to 140 C. can be used in preparing the fibers used in the filters ofthe present invention. By using the low density polyolefins a lowerbonding or fusing temperature is needed to give rigidity or firmness tothe finished plug. The high density of polyoleiins require a slightlyhigher bonding temperature be used on the filter plugs.

The particular method of manufacturing the polyolefin material is not apart of the present invention and is known to the industry concernedwith such manufacture. ln other words, the desired polyolefin materialcan be obtained from a manufacturer by giving the above specificationsof molecular Weight and other properties to such manufacturer. It willbe noted, however, that the polyolefin material used in the presentinvention is a material resistant to moisture.

After obtaining a suitable polyolefin composition it is spun intofilaments of the proper denier. The number of filaments required to makea satisfactory filter plug tow Will depend on the thickness of theindividual fibers and the amount of crimp they have been given. Ingeneral, it will require 20,000 to 40,000 filaments when the fibers arein the range of four to two denier per filament, and 2,000 to 5,000filaments when the fibers are Patented Dec. 27, 1960 described in thefollowing U.S. Patents:

Y ,used in existingequipment.

' heated metal-forming block.

in the 30 to 8 denier-per-lament range. Also with higher crimp asuitable rigid lter can be obtained with lament count toward the lowerside of the aforementioned ranges.. The exact process used forspinningthe polyolefin materials into filaments is not a limitation onthe present invention. ,Any of the methods known in the textile industryfor preparing polyolefin filaments may be used for preparing thefilaments of the present invention provided that a suitable denier Visobtained.

The filaments of suitable denier are then crimped. As indicated above inaccordance with the preferred embodiments of the present invention arelatively high degree of crimp is imparted to the laments. However, ifit is desired to make filaments somewhat similar to the prior artfilaments which have been'used for filters, a lower' degree of crimp,say a degree of crimp of the order of 6-12 crimps per inch, can be putinto the filaments of the present invention. However, when this is done,even then a superior filter will be obtained by using the polyolenmaterials ofthe present invention.

There are various types of crimping apparatus that may be used. Examplesof satisfactory crimping devices are 2,090,669, 2,311,174, 2,505,618,2,698,970, 2,734,228, 2,734,229, 2,734,251, 2,740,992 and 2,749,233.Most of the commercial crimping devices for textile tows are of thestuing-box type, although in some instances the gear type is used. Bothof these types are discussed in the patents listed above. We prefer thestuffing-box type of textile tow crimping apparatus since it readilypermits putting in a range of crimp from about six crimps per inch upto, for example, 40 crimps per inch of an amplitude between about 0.10inch and 0.01 inch.

- By crimps per inch we mean the number of convolutions per inch offiber length. By amplitude of crimps we mean the height of eachconvolution.

It is apparent from the foregoing that the actual length of a fibersegment which is expressed in terms of crimps per inch, depending uponthe number of crimps and the amplitude thereof, may, for example in asegment of one inch length in crimped form, actually occupy 1% to 2inches when in an uncrimped condition. It is apparent from this thatthere is considerable filling capacity added to the yarn when it isgiven a high degree of crimp and with the filaments of the presentinvention considerable rigidity is imparted to the resultant filter froma high degree of crimp. Y

The crimped filaments of polyolefin produced as above described and inthe form of continuous filaments can readily be fed into existingautomatic filter-making machinery. InV such .machineryV a bundle ofcrimped filaments are formed into a filter element, which element isYenclosed in the wrapper and cut into segments, which segments feed intocigarette machines to apply the filter to the cigarette. cigarettefilters as just mentioned and in accordance with presently usedoperations but there is a saving because spray booths Vand the likeparts may be omitted or not Or if it is desired the filaments; of thepresent invention may be passed into a present invention may be not onlyfused at the surface but the heat will cause some fusing Within thefilter element whereY the highly crimped laments contact one another. Bythis procedure self-contained filter elements may be manufacturedWithout the need of an external wrapperor plasticizer addition orcoating the filaments.

Hence, it is apparent that our crimped polyolefin multifilament materialof the present invention may be used in several ways to make filterelements either in presently used equipment wherein the filter'elementis encased in a wrapper or in a more simple manner Ywhere a Wrapper isnot required. Y

Tests of tobacco smoke Our material may be manufactured into i By heatthe filaments ofthe lters consisting essentially of` the continuouscrimped polyolefin filaments of thepresent invention shows that suchlter elements in accordance with the present invention will remove agreater quantity of tar and nicotine with about the same or lesspressure drop than commercial lter elements now available in theindustry.

As of assistance to a more detailed understanding of the instantinvention reference may be made to the attached drawing forming a partof the instant application. In the drawing:

Fig. 1 is an illustration on a somewhat enlarged scale of a singlestrand of polyolefin filament containing of the order of 30 crimps perinch;

Fig. 2 represents somewhat on an exaggerated scale a small section of acrimped tow before the blooming thereof, said tow being made up ofcrimped polyolefin laments;

Fig. 3 likewise illustrates on an exaggerated scale a small section ofsuch crimped tow afterit has been bloomed for the manufacture of tobaccosmoke lters therefrom; and

Fig. 4 shows the assembly of a filter in accordance with the presentinvention onto a conventional cigarette. In this ligure certain partshave been broken away in order that the interior of the filter may bebetter observed.

Since the various gures of the drawing appear readily understandable oninspection, extended description thereof appears to be unnecessary. A

A further understanding of our invention will be had from aconsideration of the following examples, with respect to which ExamplesI and II are set forth for illus-Y trating our preferred embodiment.Examples III and IV are set forth primarily for comparison purposes.That is, in orderr to compare a product generally in accordance with thepresent invention but having only a relatively low degree of crimp witha prior art product having the same amount of low crimp, Examples IIIand IV have been set forth.

EXAMPLE I Polyethylene filters-A drafted, high-density polyethylene yarnof 2.6 denier per filament was prepared by melt spinning polyethyleneusing a 50-hole spinneret with' 0.30 mm. openings. The drafted yarn hada strength of 2.9 grams per denier, a stretch of 30% and a softeningpoint around 115 C. It was plied into a tow (33,000 filaments) Yand aportion of the tow was crimped on a textile crimper which produced 18crimps per inch, all in a direction perpendicular to the length of thefibers. The crimped tow was uled out to a width of 12 inches and fedinto a filter plug-making machine which produced paper-wrapped filterplugs, mm. in length and 25.5 mm. in circumference. After being heatedfor 10 seconds at 120 C. the plugs were quite firm and Yhad an averagepressure drop (resistance to draw) of 8 inches at an air flow rate of17.5 ml. per second. Two of the plugs were cut into lengths of 15 mm.and these filter tips were attached to l0 king size cigarettes (Brand A)which had been shortened by 15 mm. These filtered cigarettes were smokedto butt lengths of 35 mm. on an automatic smoking machine similar indesign and operation to the one described by I. A. Harlan and H. R.Hanmer of Ind. and Eng. Chem. 28, 836-839 (1936). The smoke which passedthrough the filters was collected and analyzed for nicotine and tarcontent. The results of this smoking test and the pressure drop of thefiltered cigarettes before smoking are shown in Table 1.

EXAMPLE II VPolyrn'opylene yItersP-A drafted polypropylene yarn of 2-8denier per filament was prepared by melt spinning polypropylene usinga'SO-hole spinneretY with 0.30 mm. openings. The drafted yarn had astrength of 4.7 grams per denier, an elongation of 35% l,and a softeningpoint around 126 C. It was plied into a tow (30,000 fila-Y ments) -andgiven `lcritnps per inch. Thus crimped tow essere? was flufed out to awidth of 12 inches and fed into a filter plug-making machine whichproduced paper-wrapped plugs 90 mm. in length and 25.7 mm. incircumference. The plugs, after a 10 second heat cure at 135 C. werevery rm and had an average pressure drop of 7.3 inches. Two of the plugswere cut into lengths of 15 mm. and these lter tips were attached to 10king size cigarettes (Brand A), shortened by l5 mm. These filteredcigarettes were smoked to butt lengths of 35 mm. on the automaticsmoking machine and the collected smoke was analyzed for nicotine andtar content. The results of this test are listed in Table 1.

EXAMPLE III Cellulose acetate filters-For the purposes of comparison aprior art commercial cellulose acetate filter was obtained. This wasmade from a commercial grade of cellulose acetate (40% acetyl) by dopespinning into a 2.5 denier per filament yarn in the conventional manner.The finished yarn had a strength of 1.2 grams per denier and anelongation of 32% Its softening point was around 195 C. It was pliedinto a tow of 33,000 filaments and crimped to 12 crimps per inch (theamount of crimps used for commercial cellulose acetate lter tow). Thecrimped tow was converted to filter plugs (25.7 mm. circumference) whichwere heated in an oven at 150 C. for one hour. These plugs wererelatively soft and were not used -in the comparison. The other part ofthe tow was sprayed with a plasticizer (glycerol tn'acetate) until thecombined weight of the sprayed tow was 85% yarn and 15% plasticizer. Thesprayed tow was converted to lfilter plugs in the manner described.After about an hours storage time at room temperature (75 F.) theseplugs were as firm as our preferred heat-treated polyethylene andpolypropylene plugs of Examples I and II. The plasticized plugs were cutinto 15 mm. filter tips and placed on l king size cigarettes (Brand A)shortened by l mm. These filter cigarettes were smoked to butt lengthsof 35 mm. on the automatic smoking machine. The results of thisexperiment are shown in Table l.

EXAMPLE IV Polyethylene filtern-For the purposes of comparison withExample III a filter was made as set forth below (rather than by ourpreferred procedure of Examples I and Il). That is, this run wasdesigned to test a polyethylene filter at a crimp level equal to thecrimp that is usually given to cellulose acetate filters.

Hence, a portion of the polyethylene tow (33,000 filaments) of Example Iwas given only l2 crimps per inch. This crimped tow was converted toplugs, hardened, and tested as 15 mm. filter tips as described inExample I. The pressure drop of the filtered cigarettes and the amountsof nicotine and tar obtained are reported in Table 1.

Table 1 Mg. Percent Percent Type of Cigarette Av. Pres- Mg. Tar NicotineTar Re- Nico- Smoked to 35 mm. sure Drop in Snoke in Smoke moved tineRe- Butt (85 mm. of Cigar- (10 cig- (10 cig- By moved inlength) ettesarettes) arttes) Filter By (in H2O) Filter Brand A-no lter--- 3. 2 17026 Brand Alt-pclyethylene filter, Example I 4.0 110 17 35 35 Brand A-polypropylene filter, Example 1T 3. 9 112 17 34 35 Brand A-celluloseacetate filter, Example III 3.8 181 20 22 23 Brand A-prlyethylenefilter, Example IV 3.6 120 18 29 31 The results of Table 1 show that thepolyethylene and polypropylene filters removed more tar and nicotinefrom the smoke of a cigarette than the prior art filter of the samenumber of fibers and same pressurev drop. The results also indicate thatthis increased efficiency of the polyethylene and polypropylene filtersis only partly due to the presence of more crimps (18) in these filters.The polyethylene filter with the same number of crimps (l2) as theacetate filter still removed more nicotine and tar. This indicates thatpolyethylene and polypropylene fibers are better cigarette smoke filtersthan the prior art cellulosic filters. Aside from their simplemechanical operation of removing tar and nicotine particles byimpingement, our new filters can also develop an electrostatic chargewhich attracts the smoke particles to their surface.

It is believed apparent from the foregoing that we have provided arelatively efficient new and economical tobacco smoke filter. Inaddition to the advantages discussed above, our filter possesses certainother advantages. For example, the rigidity of our filter is such thatin automatic cutting machinery the cutting can readily be accomplishedwithout a fraying effect thereby giving a filter of excellent appearancewhich is free of roughness which might be noticeable if a smoker broughthis tongue against the end of the lter.

We claim:

l. A tobacco smoke filter consisting essentially of a bundle of crimpedcontinuous polyolefin fibers which fibers have been drafted, saidpolyolefin having a molecular weight between 30,000 and 200,000 and asoftening point between C. and 160 C., said fibers being of a denierbetween 2 and 8 per filament and present in the filter in an amountbetween 2,000 and 40,000 filaments, said crimp being up to 40 crimps perinch.

2. A tobacco smoke filter in accordance with claim 1 wherein the crimpis between 16 and 40 per inch.

3. A tobacco smoke filter in accordance with claim 1 wherein the surfaceof the side wall portion of the filter is fused.

4. A tobacco smoke filter element in accordance with claim l wherein thefilaments are contained in a wrapper.

5. A fibrous tobacco smoke filter comprising a plasticizer-free,transversely-cut segment of a tow of 2,000 to 40,000 continuousfilaments of 8 to 2 denier per filament of a polyolefin from the groupconsisting of polyethylene and polypropylene, the fibers of the filter(a) being generally oriented substantially longitudinally thereof, (b)having a high crimp of the order of about 18 to 40 crimps per inch, and(c) being fused to adjacent filaments at random points of contact.

6. As a new article of manufacture an improved cigarette filteressentially comprised of several thousand polypropylene filaments of adenier not greater than 8 denier per lament, the filaments having astrength of at least 4 grams per denier and an elongation of at least35%, said polypropylene filaments being highly crimped and a paperwrapper enclosing the crimped polypropylene filaments and holding themin place.

7. As a new article of manufacture a tobacco smoke filter which consistssubstantially entirely of a bundle of crimped continuous polyolefinlaments which filaments extend substantially the entire length of thefilter, a wrapper around the periphery of said bundle, said polyolefinfilaments being characterized in that they are of a denier per filamentof not greater than 8 and are crimped up to 40 crimps per inch.

8. A tobacco smoke filter in accordance with claim 7 wherein thefilaments are comprised of polyethylene which has a molecular weightabove 10,000 and below 1,000,000 and a softening point between 85 and160 C.

9. A tobacco smoke filter in accordance with claim 7 wherein the lamentsare comprised of polypropylene.

References Cited in the tile of this patent UNITED STATES PATENTS2,476,582 Browne et al July 19, 1949 (Other references on followingpage) 7 STATES PATENTS 8 Miner' -v ,f sept. 1d, 1957v MacHenry Nev. 12',1957 Kiefer et a1.V Sept. 15, 1959l FOREIGN PATENTS Austral-ia' Mar. 30,1944 Great Britain May 23, 1956 France V Apr. 13, 1955 OTHER REFERENCESThe Condensed `Chemical Dictionary, page 532, Pub lished 1950 byReinhold PublishingCorp'., New York,

Simis'o'n Oct. 4, 1949` 2,813,051?

Nicol oct. 7, 1952 904,050 MaeHe'nry Y Sept. 7, 1954 Taylor V May 3,1955 5 m 414 Knudsen Sept. 4, 1956 19"340 Knudson Oct. 9, 1956 1 1-01035 Florman 1 Dec. 18, 1956 Hackney etal; 1-3-7 E Dec. 18, 1956 lo DavisDec. 25, 1956 Touey Feb. 5, 1957 Taylor et al Apr. 23, 1957 N.Y.

1. A TABACCO SMOKE FILTER CONSISTING ESSENTIALLY OF A BUNDLE OF CRIMPEDCONTINUOUS POLYOLEFIN FIBERS WHICH FIBERS HAVE BEEN DRAFTED, SAIDPOLYOLEFIN AVING A MOLECULAR WEIGHT BETWEEN 30,000 AND 200,000 AND ASOFTENING POINT BETWEEN 85*C. AND 160*C., SAID FIBERS BEING OF A DENIERBETWEEN 2 AND 8 PER FILAMENT AND PRESENT IN THE FILTER IN AN AMOUNTBETWEEN 2,000 AND 40,000 FILAMENTS, SAID CRIMP BEING UP TO 40 CRIMPS PERINCH.